求(x+3y-3xy)-2(-2x-y+xy)的值,其中x+y=1/3,xy= -1/2
问题描述:
求(x+3y-3xy)-2(-2x-y+xy)的值,其中x+y=1/3,xy= -1/2
答
(x+3y-3xy)-2(-2x-y+xy)
=x+3y-3xy+4x+2y-2xy
=5x+5y-5xy
=5(x+y)-5xy
=5(1/3)-5(-1/2)
=5/3+5/2
=10/6+15/6=25/6